Priority service control equipment for operator positions



h 14, 59%? N. 1.. LAEFER PRIORITY SERVICE CONTROL EQUIPMENT FOR OPERATOR POSITIONS l4 Sheets-Sheet 2 Filed Oct. 23, 1963 Nuq .ul Kbb SE28 QB 53% Ex uvtwfi mbbq QED EORR DQ 3 SEE m.

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OPERATOR POS ITIONS PRIORITY SERVICE CONTROL EQUIPMENT Shea Filed Oct. 23, 1963 is-$heet .5

ESQ \IOOQ QGINO QR R E F E A L L N PRIORITY SERVICE CONTROL EQUIPMENT FOR OPERATOR POSITIONS N. L LAEFER PRIORITY SERVICE CONTROL EQUIPMENT FOR OPERATOR POSITIONS Filed Oct. 23, 1963 14 Sheets-Sheet 9 N QQ l4 Sheets-Sheet 1O EMORY N. L. LAEFER PRIORITY SERVICE CONTROL EQUIPMENT FOR OPERATOR POSITIONS Marsh 14, 3967 Filed Oct. 23.

March 14, 1967 N. 1.. LAEFER PRIORITY SERVICE CONTROL EQUIPMENT FOR OPERATOR POSITIONS Filed Oct. 23, 1963 14 SheetTSheet 11 fi h IN U 33 m I b53858 M x23 J \Stcdq E v m 4% 1 P W I E r $6 $3 .1 Tami was 865 H QQ w muw \Lmu 3Q QQQ TAGQ N62,, QQGQ WFQIU QQQ w v lfi m IE TYEG 339. ES 1 7 INTO w w A w 58 u H u 2956a E ib {lb mQ V 3a Q55 83 $13 m 8 IVS 3Q Tomb 3 2058a Cu 2E6 29835 "39% x55 Edi 1 Mamh 114;, 11967 N. L. LAEFER PRIORITY SERVICE CONTROL EQUIPMENT FOR OPERATOR POSITIONS Filed Oct. 25, 1963 14 Sheets-Sheet 12 E T1967 N. 1.. LAEFER PRIORITY SERVICE CONTROL EQUIPMENT FOR OPERATOR POSITIONS l4 Sheets-Sheet 15 Filed Oct. 25, 1963 Hub MUEQMW \CRGRE 059mm March 14 11967 N. LAEFER PRIORITY SERVICE CONTROL EQUIPMENT FOR OPERATOR POSITIONS Filed Oct. 23, 1963 14 Sheets-$heet 14 m bm nited States Patent 3,399,468 SERVHQE CQNTRGL EQUIPMENT FGR OiERATOR PUSlTiONS Norman L. Laefer, Brooklyn, N.Y., assignor to Bell Teiephone Laboratories, Incorporated, New York, N.Y., a

corporation of Jew York Filed 0st. 23, 1963, Ser. No. 318,355 Claims. (Cl. 17927) This invention relates to switching systems and particularly to switching equipment for controlling the ordered sequence in which telephone calls are connected to operator positions for service. The present invention further relates to a telephone system having groups of calling circuits each of which is entitled to request selectively both non-priority and priority connections to operator positions. This invention relates more particularly to equipment which enables all priority requesting circuits in each of the groups to be connected to an individual one of the operator positions before any non-priority requesting circuit.

The advent of advanced mechanized procedures for serving person-to-person, coin, dial 0, and other special service telephone calls has in recent years increased both the speed and versatility of telephone communications to the extent that at present, or in the very near future, customers may dial and complete such calls with a minimal amount of operator assistance. Such mechanized procedures advantageously reduce the labor content of the operators job and also provide for more convenient and efiicient telephone service at less cost to customers.

in accordance with present day procedures for serving such calls, the customer dials either the called station number together with a prefixed special service code, for example, for a person-to-person or a coin call, or simply a zero (0) for a dial 0 call. The call is then automatically extended to an appropriate trunk circuit having access to an operator position. Upon receiving such a call, the trunk circuit requests a connection to an operator position on a non-priority (routine) basis and is connected thereto for enabling an operator to furnish the required assistance. fter the needed assistance has been provided for the callin customer, the call is automatically completed to the called station and the operator position is disconnected from the calling circuit. In the event that the customer desires further assistance after the operator position has been disconnected and while the call is yet in progress, the trunk circuit may be activated, for example, by a switchhook dash to request connections to an operator position on a priority basis.

Non-priority service is requested by the trunk circuit when it initially receives a special service call because operator assistance is not required as quickly at that time as it is while the call is in progress. Priority connections to an operator position are requested by a trunk circuit while a call is in progress in order to serve customers with minimal delay and to reduce the holding time of the calling circuits.

The switching system disclosed in the A. H. Scheinrnan patent application, Ser. No. 318,360, filed concurrently herewith, provides for the connection of calling trunk circuits to operator positions on both non-priority and priority bases. In accordance with such a system, incoming trunk circuits of a tandem telephone office are segregated into trunk groups and each of the trunk circuits is provided with a pair of service requesting conductors. One of these conductors is used for requesting non-priority connections to an operator position when a call is initially received by the trunk circuit and the other is used for requesting connections to an operator position on a priority basis after the call is in progress. These trunk circuits are associated with position link connectors which asaataa Patented Mar. 14, 1%5? together with a position link controller provides for the interconnection of the circuits with operator positions. The position link connector provides the actual interconnecting means and the link controller controls the ordered sequence in which non-priority and priority requesting trunk circuits are connected through those connectors to operator positions for service.

The link controller in such a system is designed to serve only one of the trunk groups at a time. It is activated by a position link connector upon the receipt of nonpriority and priority requests to select a preferred one of the trunk groups associated with that connector and then to connect all priority requesting trunk circuits in all selected group to operator positions before any of the non-priority requesting trunk circuits in the same group.

Heretofore, the link controller has proceeded to select and effect the connection of each non-priority requesting circuit-in the selected group to an operator position immediately after all of the priority requesting trunk circuits in the same group have been connected to an operator position. Thereafter, when all of the non-priority requesting circuits in the selected group have been connected to operator positions, the controller has selected another trunk group having trunk circuits requesting connections to an operator position, and proceeded to control the connection of all priority requesting trunk circuits in that group to operator positions before any non-priority requesting trunk circuit in the same group.

No facilities were heretofore available for the foregoing type of system for connecting all of the priority requesting trunk circuits in all trunk groups to operator positions before any non-priority requesting trunk circuit in the same groups. As a consequence, trunk circuits in less preferred trunk groups of such a system may at times request priority connections to operator positions concurrently with trunk circuits in a more preferred trunk group, which are requesting both non-priority and priority connections to the same positions, and the trunk circuits in the less preferred groups are required to wait for service for a considerable time while both the priority and nonpriority requesting circuits of the more preferred group are being connected to the operator positions. It has proven undesirable under certain tIElffiC conditions to serve priority requesting trunk circuits in this manner because these circuits are customarily serving calls which are already in progress at the time that the priority service is requested. Under such conditions, the completion of calls is delayed until after the operator assistance is provided and, furthermore, customers are occasionally required to wait a considerable time before the assistance is furnished.

It may be appreciated from the foregoing that a need exists for a means of providing prompt operator assistance while special service calls are in progress by enabling all priority requesting trunk circuits in all trunk groups of the system to be interconnected with operator positions before any non-priority requesting trunk circuit in the same groups.

Accordingly, it is a general object of my invention to provide prompt operator assistance on special service calls, and particularly when such assistance is requested while the calls are in progress.

Another object is to provide improved switching equipment for serving calling circuits requesting priority connections to operator positions.

These and other objects are attained in accordance with an exemplary embodiment of my invention wherein special service calls are received at a tandem telephone ofiice by groups of incoming trunk circuits and are selectively connectable through the switching network of position link connectors to operator positions on both non-priority and priority bases. According to this exemplary embodi ment, all priority requesting trunk circuits in all trunk groups are connectable to operator positions before any non-priority requesting trunk circuit in the same trunk groups.

As in the equipment disclosed in the cited Scheinman application, each of the trunk circuits in my illustrative embodiment is equipped with a pair of service requesting leads to a position link connector. One of these leads is used for presenting a request to the position link connector that connections be established on a non-priority basis through that position link to an available position. The second lead is used by the trunk circuit to present a request to the position link connector for connections to an operator position on a priority service basis.

Each position link comprises individual non-priority and priority registers for each trunk circuit in each trunk group for registering their requests. When non-priority and priority requests have been registered in these registers and operator positions are available to serve these requesting trunk circuits, the position link bids for and is connected to an idle position link controller. After being connected to the link controller, the position link informs that controller of the identity of the trunk groups which have trunk circuits requesting non-priority and priority connections to operator positions, and the controller registers the received trunk group identities in a trunk group registration circuit. Shortly afterwards, a trunk group registration ended circuit in the controller is activated to block temporarily the registration of the identity of any other trunk group in which a trunk circuit may subsequently request service while the controller is connected to the position link. This registration ended circuit insures that trunk groups are served on an equitable basis in the approximate order in which their trunk circuits present priority and non-priority connection requests.

The link controller also includes a trunk group selection circuit which is activated by the trunk group registration circuit for selecting for service all of the identified trunk groups which have at least one priority requesting trunk circuit, before any of the identified trunk group having only one or more non-priority requesting trunk circuits. After the selection of the most preferred one of the identified trunk groups, the link controller then controls the operation of the position link to effect the connection of each priority requesting trunk circuit in that group to an operator position before any non-priority requesting trunk circuit.

In contradistinction to the Scheinman equipment and in accordance with the present invention, after the last priority requesting trunk circuit in the most preferred trunk group has been connected to an operator position, it cooperates with the trunk group registration circuit to activate a select next group circuit in the link controller. The select next group circuit, in turn, operates the trunk group selection circuit for selecting the next most preferred one of the identified trunk groups having at least one priority requesting trunk circuit. The link controller then controls the position link for effecting the connection of each priority requesting trunk circuit in the next most preferred trunk group to an operator position.

After the very last priority requesting trunk circuit has been connected to an operator position for service, it cooperates with the trunk group registration circuit to activate the select next group circuit which, in turn, operates the trunk group selection circuit for selecting a preferred one of the identified trunk groups having at least one non-priority requesting trunk circuit. The link controller thereafter controls the position link for effecting the connection of each non-priority requesting trunk circuit in this last selected trunk group to an operator position. All of the other identified trunk groups having nonpriority requesting trunk circuits are thereafter successively served in a similar manner. When all priority and non-priority requesting trunk circuits have been connected to operator positions the link controller is disconnected from the position link.

The present invention also provides a priority calls waiting circuit in the link controller which enables it to recognize any of the trunk groups in which a trunk circuit presents a priority connection request after the trunk group registration ended circuit has blocked the further registration of other trunk group identities in the trunk group registration circuit. This priority calls waiting circuit is activated while the controller is controlling the interconnection of a non-priority requesting trunk circuit with an operator position, for causing the controller to finish interconnecting that trunk circuit with a position and then to disconnect itself from the position link and thereby to restore to its idle condition. The position link serving at least one priority requesting trunk circuit may then bid for and be connected to the idle controller for effecting the registration of the identity of each trunk group which then has a trunk circuits requesting priority and non-priority service. Each of the priority requesting trunk circuits in all of the identified trunk groups is then connected to an operator position before any non-priority requesting trunk circuit in a manner as previously explained.

A feature of my invention is the provision of groups of trunks each of which is entitled to connections to a plurality of operator positions on both routine and priority bases, a registration means responsive to the receipt of routine connection requests and priority connection requests from the trunks in each of at least two of the trunk groups for registering the requests, and facilities activated by the registration means for connecting each of the priority requesting trunks in each of the groups to one of the positions before any of the routine connection requesting trunks.

Another feature of this invention is the provision of a plurality of trunks each of which has means for requesting routine and priority connections to a plurality of operator positions, a register for registering routine connection requests received from any of the trunks, another register for registering priority connection requests received from any of the trunks, selecting means responsive to the registration of routine and priority connection requests in the registers for selecting all priority requesting trunks in each of the trunk groups for connection to any one of the positions before any one of the trunks having a registered routine connection request, and facilities activated by the selecting means for connecting each selected trunk to one of the positions in the order in which it is selected.

A further feature, directly related to the immediately preceding one, is the provision in the selecting means of circuitry responsive to the registration of routine and priority connection requests in the registers for initially selecting for service one of the groups of trunks having at least one priority request, and control circuitry for controlling the connecting facilities to connect successively each priority requesting trunk of the selected group to one of the positions; and the further provision of advancing circuitry which is activated immediately after the last priority requesting trunk in the selected group has been connected to one of the positions for advancing the selecting means to select for service another group of trunks having at least one registered priority request in one of the registers, and thereby to serve priority requesting trunks before any routine connection requesting trunk.

Yet another feature is the provision in the selecting means of circuitry activated immediately after the last priority requesting trunk in all the trunk groups has been connected to one of the positions for advancing the selecting means to select for service one of the trunk groups having a registered routine connection request,

Still another feature of the present invention is the provision of a trunk group registration circuit for registering the identity of each of the trunk groups requesting non-priority and priority connections to an operator position, a trunk group registration ended circuit for tens.-

porarily blockin the further registration of trunk group identities in the group registration circuit after a predetermined interval, and a priority request waiting circuit for recognizing any of the trunk groups in which a trunk circuit presents a priority connection request after the registration ended circuit has blocked the further registration in the trunk group registration circuit and for thereafter enabling the control circuitry to effect the connection of these priority requesting trunk circuits to operator positions before non-priority requesting trunk circuits in trunk groups which have already registered their identity in the trunk group registration circuit.

An advantage of my invention over the prior art is that groups of trunk circuits having means for requesting both non-priority and priority connections to operator positions may request priority connections to such positions and be connected thereto with minimum delay. The present invention minimizes delay because trunk circuits in each of the trunk groups, which are requesting priority connections to operator positions, are connected thereto before any non'priority requesting trunk circuit.

The foregoing objects, features, and advantages, as well as others, of my invention may become more apparent from a reading of the following description with reference to the drawing in which:

FIG. 1 shows, in block diagram form, the equipment of a tandem telephone system in which the equipment illustrative of the principles of the present invention has been embodied;

FIG. 2 is a block diagram depicting the equipment of the illustrative embodiment and comprises a group of ten position link connectors employed in the tandem telephone system for connecting 500 incoming trunk circuits to 66 operator positions through position control circuits and position circuits under control of three position link controllers and a trafiic regulator;

FIGS. 3-14 inclusive, show in block and schematic form the essential circuit details of an incoming dial 0 trunk circuit, a special service trunk circuit, a position link connector, a position link controller and a trafiic regulator comprising the equipment utilized for connecting incoming calls to operator positions on both non-priority and priority bases; and

FIG. 15 depicts the position in which FIGS. 1, 2 and 314 should be placed to show the cooperation among the equipment units.

It is noted that FIGS. 3l4 employ a type of schematic notation referred to as detached contact in which an X crossing a line represents a normally opened contact of a relay and a bar crossing a line represents a normally closed contact of a rela; normally referring to the unoperated condition of a relay. The principles of this type of notation are described in an article entitled An Improved DetachedContact Type Schematic Circuit Drawing by F. T. Meyer in the September 1955 publication of the American Institute of Electric Engineers Transactions, Communications and Electronics, Vol. 74, pp. 505-513.

Each relay contact is designated in the drawing in a manner which indicates the relay of which it is a part and as well uniquely identifies it with respect to other contacts of the relay. For example, referring to relay contact M0tl1 of FIG. 3, it is noted that the M00 part of the designation indicates that it is controlled by the re lay Mtifl of FIG. 3 and the l uniquely identifies it with respect to the other contact Miifi-2 of relay MM the latter contact being shown on PEG. 4.

In the drawing, simplified schematic circuit patterns of relay contacts, which are known in the art as symmetries, have been depicted in the drawing in block diagram form. According to such patterns, the contacts are arranged to furnish one output signal if a certain combination of relays is operated at the same time. For example, FIG. 10 shows two symmetrics disclosed in block diagram form. In the one symmetric associated with relay ATK of FIG.

10, a ground signal will be applied to the winding of relay ATK through the symmetric of contacts on the five relays ATfl-AT4 of FIG. 10 if and only if one of the latter relays is operated. In the symmetric associated with the relays AGK and AGKA of FIG. 10, a ground signal will be applied to the windings of the latter relays if and only if one of the 10 relays AGG-AG9 of FIG.10 is operated. The geometric configurations of the contacts in each of these blocks used in the present drawing are not shown for they are well known in the art. For details on the construction of such configurations, reference may be made to Keister, Ritchie and Washburn, The Design of Switching Circuits (5th ed., 1951).

The equipment of the present information may be advantageously incorporated in an automatic tandem telephone system wherein common control circuits are employed to control the establishment of calls through a switching network. One such system is disclosed in R. B. Curtis patent application, Serial No. 318,275, filed concurrently herewith. It is to be understood, however, that the present invention is not limited to use with a telephone system of this type, but that it may also be utilized with other types of switching systems, such as local or toll systems.

The equipment illustrative of the principles of the present invention has been embodied in a tandem telephone system of the type disclosed in the cited Curtis application (hereinafter referred to as the Curtis disclosure). It is particularly concerned with the apparatus in the dial 0 trunk circuits, the special service trunk circuits, the position link connector and position link controller circuits, as well as the other circuits shown in heavy lines on FIGS. 1 and 2. The other equipment units are neither shown nor described in detail herein, except where necessary, for a complete understanding of this invention. Structural details of the trafiic regulator circuit of FIG. 2 are set forth in the C. E. Germanton patent application, Ser. No. 318,427, filed concurrently herewith. The cited Curtis and Germanton applications may be consulted for a complete understanding of the construction and operation of the units not covered in detail herein.

GENERAL DESCRIPTION The general organization of the principal equipment units of the illustrative embodiment of my invention will now be described with reference to FIGS. l and 2. The crossbar tandem system as disclosed in the aforementioned Curtis disclosure is designed to serve several different classes-of-calls, such as dial 0 assistance calls and other special service calls, such as person-to-person and coin calls. These types of calls are extended to the tandem system from an originating office, such as ofiice OR, via incoming trunks, such as the dial 0 and special service trunks TK'Ot) and TK94. Each of the latter trunks is illustrative of the numerous trunks provided in a fully equipped tandem system for serving each of the different classes-of-calls. The trunks TKitt and TK94 are terminated individually in the incoming trunk circuits TCflt) and TC94.

Each of the latter trunk circuits has five major ap pearances in the switching network of the tandem system. One appearance is on the trunk frame TLF and is used for establishing the talking connections between the calling and called stations. A second appearance is on the sender link SL and is used for passing information to and from the common control equipment, such as the sender S and marker M, of the system. Another appearance is in the call data recording equipment CDR and is used for recording the details required for charging for calls. A fourth appearance is in the data transfer circuit DT and is used for facilitating the interchange of data among the trunk circuits, common control circuits, and the position control circuits, such as circuit PCC. The fifth appearance is in the operator position link connector circuit, such as circuit PLO, and is used for connecting the trunk circuits to operator positions on non-priority and priority bases.

In this illustrative embodiment of my invention, the dial and special service trunk circuits, such as circuits TCGOTC94, are segregated according to the classof-calls which they serve. There are a maximum of ten groups in each position link connector. Each such group comprises only trunk circuits that serve the same class-ofcall. There are five trunk circuits in each trunk group. This arrangement facilitates the control over the circuit operations involved in interconnecting the trunk circuits with operator positions and permits the circuits in each class-of-service group to be served on an equitable basis.

For requesting connections to the operator positions on non-priority and priority bases, each of the dial 0 and special service trunk circuits, such as circuits TCGJ- TC94, is equipped with non-priority and priority start leads, such as the leads NPSfi-NPS94 and PSOPS94, respectively. The trunk circuits may selectively request connections to the operator positions either on a nonpriority (routine) basis or a priority basis by applying a service request signal to the appropriate non-priority or priority start lead.

It may be seen in FIG. 2 that the position link connector and the position link controller circuits, such as circuits PM) and LC(), together provide the means for interconnecting the dial 0 and special service trunk circuits, such as circuits TCQti-TC94, with operator positions, such as positions 0P1 and OP66, via position control circuits and position circuits, such as the circuits FCC and PC. The position link connectors comprise the actual interconnecting means while the position link controller, as its name implies, controls the operations of a position link in such a fashion that all of the calling trunk circuits are interconnected with operator positions on an equitable basis.

The position link, such as link PLO, includes individual non-priority and priority registers, such as the registers NPRl-NPRH) and PR1PR10 of FIG. 2, for each of the class-of-service trunk groups for registering nonpriority and priority service requests received from the associated fifty trunk circuits. Non-priority requests are received from the dial 0 and special service trunk circuits over the leads NPS-and are applied to the nonpriority registers, such as registers NPRl-NPRli), through the individual class-of-service gate circuits, such as the circuits CGl-CGIG. Each of these gate circuits is controlled by a traflic regulator circuit TR in order to insure that the dial 0 and special service calls received by the incoming trunk circuits are served in the approximate order in which they are presented for service.

Priority service requests from dial 0 and special service trunk circuits are received over the priority start leads PS and are registered in priority registers, such as the register PRl-PRIG, independently of the gating system employed for the registration of non-priority requests. As a consequence, the latter registers are effective, as hereinafter explained, to activate a position link controller for allowing the priority requesting trunk circuits to be interconnected with operator positions before any of the non-priority requesting trunk circuits.

As is indicated in FIG. 2, each position link connector in the presently disclosed embodiment has a maximum of fifty trunk circuits connected to its input and 198 position loops connected to its out-put. Illustrative of the latter arrangement is the connection of the trunk circuits TC00-TC49 (fifty trunk circuits) to the input of the position link PM) and the position loops iii-L197 to the output of link PLG. For connecting the trunk circuit information and control leads, such as the leads of the cables ICC!) and ICC94 of FIG. 2, the position loops, each position link employs a three-stage crossbar switch network comprising a primary, secondary and tertiary switching stage, such as the stages'PRi, SEC and TER in the position link PLii of FIG. 2. The linkages connecting the primary and secondary stages PRI and SEC are designated A links and the linkages connecting the secondary and tertiary stage SEC and TER are designated B links.

The position link connector circuit, such as circuit PLii, may be referred to for simplicity in the following description as position link PLti or as link PL-i Accordingly, this terminology is used extensively throughout the remainder of the specification. The position links are arranged together into link groups, each of which comprises ten position links. An arrangement of the position links forming one such link group and the association of those links with incoming trunk circuits, position link controllers, operator positions, a traffic regulator and other control circuits is illustrated in FIG. 2.

Three link controllers are provided for each link group to control the ten position links. Preference and allotter circuits (not shown) are included in each of these link controllers to insure that equitable service is given to the incoming call tratfic on each position link of a group as Well as to insure that the incoming calls will be equitably distributed to the available positions. Each link controller comprises a trunk group selection circuit (not shown) for selecting each trunk group having at least one priority requesting trunk circuit before any trunk group having a trunk circuit requesting only nonpriority service. In addition, each link controller provides for selecting each priority requesting trunk circuit in a selected trunk group before any non-priority requesting trunk circuit in the same group. Each link controller also includes a select next group circuit (not shown in FIGS. 1 and 2 but shown schematically in FIG. 14) which provides for the connection of all priority requesting trunk circuits to the operator positions before any non-priority requesting trunk circuit. To do so, the select next group circuit is activated immediately after the last priority requesting trunk circuit in a selected trunk group has been connected to an operator position (that is, before any non-priority requesting trunk circuit in the selected group is served) for operating the trunk group selection circuit (not shown in FIGS. 1 and 2 but shown schematically in FIG. 10) to select for service another trunk group which has at least one priority requesting trunk circuit. The select next group circuit also is activated to advance the trunk group selected circuit to select for service a trunk group having at least one nonpriority requesting trunk circuit after the last priority requesting trunk circuit in all trunk groups has been connected to an operator position.

As is illustrated in FIG. 2, a group of 66 operator positions is connected to the ten position link PLti-PL9 of a link group via individual position circuits and position control circuits as well as the aforementioned 198 position loops. The latter loops are divided into 66 groups, each of which comprises three loops. A loop group, such as group LGl comprising the loops Lit-L2, is individually associated with one of the 66 position control circuits, such as circuit PCC. Thus, a link group serves to interconnect any one of 500 incoming trunk circuits with any one of 66 position control circuits via 198 position loops.

Each operator is provided with a position unit, such as unit PUT of FIG. 2, which comprises a position control circuit and a position circuit. These circuits, together with the equipment at the operator position, provide three loop circuits whereby an operator may serve calls. A position control circuit, such as circuit PCC of 2, includes facilities for automatically conditioning each of the associated loops for connecting calls one-oy-one through the position circuit to the operator position. The control circuit also comprises apparatus for enabling an operator to connect her telephone to any calling loop and to place a hold condition on any calling loop while she serves a call on another loop. A key-control position accuses control circuit, such as circuit KCP of FIG. 2, is provided for each link group and is used for selectively preconditioning the control circuits of the position units, such as units PU1PU56, for serving one of the different classes-of-calls receivable from the incoming trunk circuits.

The position control circuit PCC, the position circuit PC and the operator position 0P1 are shown to comprise three ditferent equipment units, rather than one, only because each of the three may be physically separated from the other two by varying distances depending upon the requirements of the office. However, for simplicity in discussion and ease of understanding, these three circuits may be generally referred to as the operator position circuit.

An operator can actively serve only one call at a time in this exemplary embodiment even though three loops, such as loops Lil-L2, are provided. In addition, when an operator is actively serving a call on one loop, the position link appearances of the remaining two loops will appear busy and no calls will be otfered to these loops at that time. Three loop circuits are provided for each position because, on some of the calls, the calling loop may be utilized for the entire duration of the call. Accordingly, if only one loop circuit was provided and it was utilized for serving such a call, the operator would be idle and would have no functions to perform for the duration of the call after she had completed the services required of her in connection with the establishment of that call. By providing the three position loops, a call can be offered to any idle loop while another loop in the same group is being utilized on another call for which the operator has completed the active servicing thereof. To facilitate the serving of such a call on the idle or unused loop, the position control circuit changes the busy condition on the position link appearances of the un used loops to an idle condition after the operator completes the active servicing of a call. Thus, the serving of the 198 position loop circuits by 66 operator positions enables a plurality of incoming calls to be extended to and served by a plurality of operators with a minimum of waiting time between calls.

A trafiic regulator circuit, such as circuit TR of FIG. 2, regulates the equitable distribution of calls from all trunk groups in the same link group to the operator positions. The regulator controls the distribution by ascertaining the service demands by the various incoming trunk circuits as well as the availability of operator positions to serve these demands. It accomplishes the regulation by controlling the gate circuits, such as circuits CGl-CGIO of FIG. 2 associated with the non-priority registers in the position link, and by controlling the position availability signals which it supplies to those position links.

The regulator comprises facilities for controlling the gate circuits to admit service requests from a group of calling trunk circuits into the non-priority registers in the position link in order that the trunk circuits may be connected on a non-priority basis to the operator positions. After the requests have been admitted and registered, the regulator closes the gates in all ten position links controlled by the regulator to lock out from those links all other trunk circuits which are in the same class-of-service trunk groups as the circuits having already registered nonpriority requests and which may subsequently request nonpriority connections to operator positions. This insures that incoming calls requesting the same class-of-service are served in the approximate order in which they are received at the tandem office. After the closure of the latter class-of-service gates, the regulator allows nonpriority service requests from trunk circuits in other classof-service groups to be admitted and registered in the position links and these latter trunk circuits may compete for connections to the operator positions with the other trunk circuits which have previously registered nonpriority service requests.

The trafiic regulator also comprises circuitry which cooperates with all of the associated position links and link controllers to provide for the connection of trunk circuits to operator positions on a priority basis. When a trunk circuit requests priority service, the regulator circuitry is activated to make all operator positions appear busy to all position links which are not associated with a trunk circuit requesting priority service, while at the same time allowing the available positions to appear idle to the position link associated with the priority requesting trunk circuit. As a result, the priority requesting trunk circuit is connected through a position link to a available position before any trunk circuit requesting non-priority service, as hereinafter explained.

Non-priority (routine) request Referring to FIGS. 1 and 2, a general description is now presented of the manner in which the incoming trunk circuits are connected through -a position link to available operator positions on a non-priority basis. It is presently contemplated that each calling customer will dial a directing digit or code to enable the originating office OR to determine whether dial 0 operator assistance or special service is required on the call, and to route it to the tandem ofiice over the appropriate one of the trunks, such as trunks TKfilL-TK94. The specific dialing routine employed for any of the calls depends upon a number of factors including whether or not a call may be completed on a customer-dialed basis to the called station.

For simplifying the description of the non-priority service features of the present invention, as well as the priority service features described in the next section, it is convenient to describe the manner in which a dial 0 call is served. This description will serve as well to explain the manner in which the other special service trunk circuits are connected to operator positions on non-priority and priority bases since the circuit operations are essentially the same for the dial 0 and special service trunk circuits. Additionally, let it be assumed that the call data recording is to be accomplished at the tandem oflice and that the originating oflice OR is not equipped for automatic calling number identification (ANI). As a result, such a call will be routed to an operator at the tendem ofiice and She must orally obtain the calling station numb er from the caller. Such a call is referred to as a dial 0 non-ANT call in the aforementioned Curtis disclosure.

On a dial 0 call, this particular originating office OR recognizes from the dialing of the initial digit 0 that the called station digits will not be dialed by the calling party, and it immediately establishes connections to a trunk; for example trunk TKGO, extending to the tandem oflice. The call is then received in the dial 0 trunk circuit TCtit) which exclusively serves calls of this type and which immediately upon its seizure requests connections to an operator position on a non-priority basis by applying a service request signal to the non-priority start lead NPSfi.

If no other dial 0 trunk circuit in the same link group as trunk circuit TC00 has previously requested, and is yet awaiting, connections to an operator position, the dial 0 class-of-service gate circuit CGI of FIG. 2 in the position link PLt admits the non-priority request from trunk circuit TCBG into the non-priority register NPRl for registration. On the other hand, if another dial 0 trunk ClfClllt in the same link group as circuit TCOO has previously registered a request in the register NPRl and it has not been connected to an operator position, the gate circuit CGl will have been activated by the trafiic regulator TR of FIG. 2 to block the registration of the non-priority request from circuit TCOG until after the previously registered request has been served.

After the service request from trunk circuit TC00 has been admitted and registered, the other control circuits of the position link PLO are activated to send class mark data to the trafiic regulator TR for informing it that a dial 0 class-of-service has been requested. This data enables regulator TR to activate the class-of-service gate circuit CO1 and the other gate circuits, which correspond to the gate circuit CGI, in all ten position link connectors of the link group. When activated, these gates temporarily block the registration of non-priority service requests from all other dial trunk circuits (not shown) which may subsequently request non-priority connections to operator positions while the trunk circuit TCtlfi is awaiting such connections. The blocking condition then persists until after the servicing of the request from trunk circuit T C60 and all of the non-priority requests which may have been simultaneously registered in the dial 0 non-priority registers for other dial 0 trunk circuits in the same link group. This gating system insures that the calls requesting the same class-of-service are served in the approximate order in which they are presented for service.

Before explaining further details of the manner in which the dial 0 call in trunk circuit TC00 is extended to an operator position, it is advisable to explain that the traffic regulator TR maintains a constant check on all 66 position control circuits, such as circuit PCC, to ascertain if operator positions are available to serve the different classes-of-calls. It may be recalled that the operator positions are selectively preconditioned for serving some or all of the classes-of-calls under control of the key-control position control circuit KCP. This checking operation provides for the eflicient use of the associated three link controllers. The efficiency is achieved because the regulator TR, after it has checked the availability of the positions, sends position availability si nals to all ten position links and accordingly allows each such link to seize one of the three controllers only if an operator is available to serve a call on a trunk circuit having a requestregistered to that link.

Thus, if a non-priority request from a first trunk circuit, such as a dial 0 trunk circuit, is registered in a first position link and the call on that circuit cannot be served due to the unavailability of an appropriate operator position to serve dial 0 calls, the regulator prevents that position link from seizing an idle link controller until after an appropriate position becomes available. On the other hand, however, if a second trunk circuit request, such as a request from a special service trunk circuit, is thereafter registered in a second position link in the same link group and a position is available to serve the call on that trunk circuit but not the call on the first dial 0 trunk circuit, the regulator TR allows the second, but not the'first, position link to seize an idle link controller. This mode of operation prevents the unnecessary tie-up of the link controllers by trunk circuits which cannot be served. In addition, it increases the speed of establishing connections and insures that calls are served quickly when there are operator positions available to serve them.

Returning now to the description of the manner in which the trunk circuit TC00 is connected to an operator position on a non-priority basis, it is noted that when the regulator TR informs the position link PLO that at least one position is available to serve the call on trunk circuit TC00, the link PLO seizes an idle link controller, for example controller LCO, and transfers to it the identity of trunk circuit TCM together with all other trunk circuits on that link which are currently requesting connections on a non-priority basis to available operator positions. Controller LCO then selects the most preferred class-of-service trunk group from among those requesting the non-priority service and then selects the most preferred calling trunk circuit, for example circuit T C00, within the selected group for connections to an available position. It should be kept in mind at this point that, in making the trunk group selection, no priority service requests are in the system at that time. Thereafter, the controller LCO informs the position link PLO that trunk circuit TCilti is to be served. In return, that link transmits back to the controller LCO a dial 0 class-of-service indication for trunk circuit TCOi) for enabling the controller LCO to initiate the selection of an appropriate operator to serve the call.

After selecting an available operator position, for example position 0P1, controller LCil scans all possible communication channels through the primary, secondary and tertiary switching stages PRI, SEC and TER and A and B links of the position link PL!) to find an idle channel capable of interconnecting trunk circuit TCiitl with an idle one of the three loops to position 0P1. When an idle channel has been found, controller LCO activates the stages PR1, SEC and TER to interconnect trunk circuit TClii) and a position loop circuit through the position control circuit PCC and position circuit PC to position 0P1. Controller LCO then releases. At the same time, the position control circuit PCC seizes the data transfer circuit DT, which then interconnects the trunk circuit TCGi) with control circuit PCC in order that circuit TCtli) may transmit class mark information to circuit PCC. Shortly afterwards, the data transfer circuit releases. The established connections are thereafter held under the control of the control circuit PCC.

Following the interconnection of trunk circuit TCOi) and control circuit PCC, the operator telephone (not shown) is operatively associated with the call connections and a tone signal is sent from circuit PCC to that telephone for alerting the operator to the call. At the same time, indicator lamps (not shown) are lit at the position to notify the operator of the class-of-call to be served and the identity of the loop engaged for that call. The operator may now orally request from the calling party both the calling and called station numbers and key both of these numbers into registers (not shown) at her position. She then depresses a position key (not shown) which causes the trunk circuit TCiiil to seize a sender, for example sender S, through the sender link SL. The depressed position key (not shown) also causes the data transfer circuit DT to interconnect the trunk circuit TCGO the position OPl and the sender S in order that the calling and called numbers and other information registered in the position control circuit PCC may be transmitted to the sender S of FIG. 1.

In response to the successful receipt of the call informa tion in the sender S, the data transfer circuit DT is released. At the sarne time, sender S seizes a marker, such as marker M, via the marker connector MC, and transmits to marker M the information it needs to extend call connections from trunk circuit TC00. Marker M selects an idle outgoing trunk circuit, for example circuit OTC, extending to the called destination and then selects and closes connections between trunk circuits TCiltl and OTC via the trunk link and ofiice link frames TLF and OLF. Once the latter connections are established, marker M releases and sender S outpulses to the next telephone ofiice the information required by that office to complete the call. The sender S then releases, thereby leaving the connections within the tandem ofiice under control of the trunk circuit TC00.

While the last mentioned circuit operations are in progress, the operator may depress a key at her position to initiate the recording of the proper call charges in the call data recording equipment CDR in a manner discussed in the Curtis disclosure and then to release the loop circuit connecting her position to the call connections. Upon the release of this loop circuit, another call may be connected thereto in a manner as described in the foregoing paragraphs. As a result of releasing the loop circuit, that circuit is not tied up during the periods when operator assistance is not required by the customer and the operator is free to utilize these facilities to serve another call while the just-served call is in progress. In the event that the customer involved on the latter call again requires assistance, she may recall the same or another on- 

1. IN COMBINATION, A PLURALITY OF OPERATOR POSITIONS, GROUPS OF CALLING CIRCUITS, EACH ONE OF SAID CIRCUITS HAVING MEANS FOR INITIALLY REQUESTING ROUTINE CONNECTIONS TO ANY OF SAID POSITIONS UPON THE RECEIPT OF A CALL AND MEANS FOR SUBSEQUENTLY REQUESTING PRIORITY CONNECTIONS TO ANY OF SAID POSITIONS DURING SAID CALL AND AFTER SAID ONE CIRCUIT HAS BEEN DISCONNECTED FROM SAID POSITION, MEANS RESPONSIVE TO THE RECEIPT OF ROUTINE CONNECTION REQUESTS AND PRIORITY CONNECTION REQUESTS FROM SAID CIRCUITS IN EACH OF AT LEAST TWO OF SAID GROUPS FOR REGISTERING SAID REQUESTS, AND MEANS ACTIVATED BY SAID REGISTERING MEANS FOR CONNECTING EACH OF SAID PRIORITY REQUESTING CIRCUITS TO ONE OF SAID POSITIONS BEFORE ANY OF SAID ROUTINE CONNECTION REQUESTING CIRCUITS. 